Power Plant Engineering

Ans.
THEORETICAL PROBLEMS
1. Define: load factor, utility factor, plant operating factor, capacity factor, demand factor and
diversity factor.
2. What is the difference between demand factor and diversity factor?
3. What is ‘diversity factor’ ? List its advantages in a power system.
4. Prove that the load factor of a power system is improved by an increase in diversity of load.
5. What is meant by load curve? Explain its importance in power generation.
6. Differentiate ‘dump power’, ‘firm power’ and ‘prime power’.
7. Define ‘depreciation’ and explain its significance.
8. Explain the sinking fund method of calculating the depreciation.
9. Discuss the factors to be considered for, ‘plant selection’ for a
10. How ‘load duration curve’ is obtained from ‘load’ curve ?
11. What are the principal factors involved in fixing of a tariff?
NUMERICAL PROBLEMS
12. The following data is available for a steam power station:
Maximum demand = 25,000 kW; Load factor = 0.4; Coal consumption = 0.86 kg/kWh; Boiler
efficiency = 85%; Turbine efficiency = 90%; Price of coal = Rs. 55 per tonne.
Determine the following:
(i) Thermal efficiency of the station.
(ii) Coal bill of the plant for one year.
[Ans.
(i) 76.5% (ii) Rs. 41,43,480]
13. The annual peak load on a 30 mW power station is 25 mW. The power station supplies load
having maximum demands of 10 mW, 8.5 mW, 5 mW and 4.5 mW. The annual load factor is
0.45. Find:
(i) Average load
(ii) Energy supplied per year
(iii) Diversity factor
(iv) Demand factor.
[Ans.
(i) 11.25 mW (ii) 98.55 × 10
6
kWh (iii) 1.12 (iv) 0.9]
14. A power station has a maximum demand of 15 mW, a load factor of 0.7, a plant capacity
factor of 0.525 and a plant use factor of 0.85. Find:
(i) The daily energy produced.
(ii) The reserve capacity of the plant.

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POWER PLANT ECONOMICS AND VARIABLE LOAD PROBLEM
141
(iii) The maximum energy that could be produced daily if the plant operating schedule is
fully loaded when in operation.
[Ans.
(i) 252,000 kWh (ii) 5,000 kW (iii) 296,470 kWh]
15. Determine the annual cost of a feed water softener from the following data: Cost = Rs. 80,000;
Salvage value = 5%, Life = 10 years; Annual repair and maintenance cost = Rs. 2500; Annual
cost of chemicals = Rs. 5000; Labour cost per month = Its. 300; Interest on sinking fund
= 5%.
[Ans.
Rs. 17,140]
16. Calculate the unit cost of production of electric energy for a power station for which data are
supplied as follows :
Capacity
= 50 MW
Cost per kW
= Rs. 600
Load factor
= 40%
Interest and depreciation = 10%
Cost of fuel, taxation and salaries = Rs. 36 × 10
11
.
[Ans. 3.71 paise]
17. Estimate the generating cost per unit supplied from a power plant having the following data :
Plant capacity = 120 MW
Capital cost = Rs. 600 × 10
6
Annual load factor = 40%
Annual cost of fuel, taxation, oil and salaries = Rs. 600,000 Interest and depreciation = 10%
[Ans. 1.33 paise]
18. Estimate the generating cost per unit. supplied from a power plant having data :
Output per year = 4 × 10
8
kWh
Load factor = 50%
Annual fixed charges = Rs. 40 per kW
Annual running charges = 4 paise per kWh
19. A 50 MW generating station has the following data:
Capital cost = Rs. 15 × 10
5
Annual taxation = Rs. 0.4 × 10
5
Annual salaries and wages = Rs. 1.2 × l0
6
Cost of coal = Rs. 65 per tonne
Calorific value of coal = 5500 kcal/kg.
Rate of interest and depreciation = 12%,
Plant heat rate = 33,000 kcal/kWh
at 100% capacity and 40000 kcal/kWh at 60%.
Calculate the generating cost/kWh at 100% and 60% capacity factor.

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